JP6698599B2 - Ground fault detector - Google Patents

Description

  The present invention relates to a ground fault detection device using a flying capacitor.

  In a vehicle such as a hybrid vehicle having an engine and an electric motor as a drive source, or an electric vehicle, a battery mounted on a vehicle body is charged and electric power supplied from the battery is used to generate a propulsive force. Generally, a battery-related power supply circuit is configured as a high-voltage circuit that handles a high voltage of 200 V or higher, and in order to ensure safety, the high-voltage circuit including the battery is electrically insulated from the vehicle body that is a ground reference potential point. It has a non-grounded configuration.

  Further, there is a vehicle provided with a booster circuit that boosts a positive potential of a battery and supplies the positive potential of the battery to the load in order to improve drive efficiency of the load. In a vehicle equipped with a booster circuit, the output of the battery, that is, the primary side of the booster circuit, as well as the output of the booster circuit, that is, the secondary side, are electrically insulated from the vehicle body and are ungrounded. The configuration is such that it is not used as the ground for the battery and booster circuit. Therefore, in a vehicle having a booster circuit, in order to monitor the ground fault condition, it is necessary to detect not only the insulation resistance between the battery and the ground but also the insulation resistance between the secondary side of the booster circuit and the ground. ..

  Therefore, in order to monitor the ground fault condition between the vehicle and the system provided with the battery and the booster circuit, specifically, the main power source system from the battery to the load such as the electric motor via the booster circuit, the ground fault is detected. A detection device is provided. A method using a capacitor called a flying capacitor is widely used for the ground fault detection device.

  FIG. 7 is a block diagram showing a configuration example of a conventional grounding-fault detecting device 500 of the flying capacitor type. The ground fault detection device 500 is a device that is connected to a non-grounded battery 520 and detects a ground fault in a system in which the battery 520 and the booster circuit 530 are provided. The ground fault detection device 500, the booster circuit 530, the load 540, and the like are controlled by the external control device 510 that is a higher-level device.

  Here, the insulation resistance between the battery 520 output side, that is, the primary side positive electrode and ground is represented by RLp1, and the insulation resistance between the negative electrode and ground is represented by RLn1. Further, the insulation resistance between the positive electrode on the output side of the booster circuit 530, that is, the secondary side, and ground is represented by RLp2, and the insulation resistance between the negative electrode and ground is represented by RLn2. The positive electrode side insulation resistance RLp is a combined resistance of RLp1 and RLp2, and the negative electrode side insulation resistance RLn is a combined resistance of RLn1 and RLn2. The combined resistance of the positive electrode side insulation resistance RLp and the negative electrode side insulation resistance RLn becomes the system insulation resistance RL.

  The capacitor C1 functioning as a flying capacitor is charged in a path formed by turning on and off the switches S1 to S4, and the charging voltage is measured by the control device 501.

  As a method of acquiring the insulation resistance RL, V0, Vcn, and Vcp are measured, (Vcn+Vcp)/V0 is calculated, and insulation resistance is obtained by referring to table data created in advance based on the obtained calculated value. Techniques for calculating RL are known. When the obtained insulation resistance RL is lower than a predetermined reference value, the ground fault detection device 500 determines that a ground fault has occurred and outputs a warning to the external control device 510.

  Here, V0 is a value corresponding to the voltage of the battery 520 measured on the path formed by turning on the switch S1 and the switch S2. Vcn is a voltage value including the influence of the negative electrode side insulation resistance RLn measured in the path formed by turning on the switch S1 and the switch S4. Vcp is a voltage value including the influence of the positive electrode side insulation resistance RLp measured in the path formed by turning on the switches S2 and S3.

  Generally, in the ground fault determination, V0 measurement, Vcn measurement, V0 measurement, and Vcp measurement are performed as one cycle, and at the time of switching of each measurement, the switch S3 and the switch S4 are turned on to form a capacitor C1 in a path formed. The charging voltage is read and the capacitor C1 is discharged.

JP, 2005-206784, A

  When the switch S1 and the switch S4 are turned on to measure Vcn while the booster circuit 530 is performing the boosting operation, the grounded side plate of the capacitor C1 receives the boosted voltage as the positive side insulation resistance RLp. A voltage divided by the negative electrode side insulation resistance RLn is applied.

  When this voltage becomes higher than the voltage applied from the positive electrode side of the battery 520, the current sneak causes the capacitor C1 to be charged with a polarity opposite to the normal polarity. In this case, the voltage measured by the control device 501 becomes 0, and the insulation resistance RL cannot be calculated. For this reason, in a system with many boosting states, there is a problem that the chances of insulation resistance calculation decrease due to the current sneak from the secondary side.

  Therefore, it is an object of the present invention to suppress a decrease in insulation resistance calculation opportunities in a ground fault detection device that includes a booster circuit.

In order to solve the above problems, the ground fault detection device of the present invention is connected to a non-grounded battery that supplies power to a load through a booster circuit, and calculates the insulation resistance of the system in which the battery is provided to calculate the ground resistance. A ground fault detection device for detecting a fault, comprising a capacitor that operates as a flying capacitor, the battery, a V0 measurement path including the capacitor, a negative side that is an insulation resistance between the battery, the battery negative side, and ground. A switch group that switches between an insulation resistance, a Vcn measurement path that includes the capacitor, a positive side insulation resistance that is an insulation resistance between the battery, the battery positive side and ground, and a Vcn measurement path that includes the capacitor. The Vcn measurement path is used when calculating the insulation resistance based on a bypass resistance connected in parallel with the negative side insulation resistance via an open switch and a charging voltage measurement value of the capacitor in each measurement path. And a control unit that switches the normally open switch to a closed state and measures the charging voltage of the capacitor in the Vcn measurement path when the measured charging voltage value of the capacitor in 0 is regarded as 0. Characterize.
Here, the control unit uses the charging voltage measurement value when the charging voltage measurement value of the capacitor in the Vcn measurement path when the normally open switch is switched to the closed state is not regarded as 0. The positive side insulation resistance can be calculated.
In addition, when the charging voltage measurement value of the capacitor in the Vcn measurement path when the normally open switch is closed can be regarded as 0, based on the step-up ratio by the step-up circuit and the bypass resistance value, The maximum value of the positive side insulation resistance can be calculated.

  According to the present invention, it is possible to suppress a decrease in insulation resistance calculation opportunities in a system ground fault detection device including a booster circuit.

It is a block diagram which shows the structure of the ground fault detection apparatus which concerns on this embodiment. It is a figure explaining the measurement cycle of a ground fault detection device. It is a figure explaining the measurement route of a V0 measurement period. It is a figure explaining the measurement course of a Vcn measurement period. It is a figure explaining the measurement course of a Vcp measurement period. It is a flow chart explaining insulation resistance calculation operation in the ground fault detection device concerning this embodiment. It is a block diagram which shows the structural example of the conventional ground fault detection apparatus of a flying capacitor system.

  A ground fault detection device that is an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the ground fault detection device 100 of this embodiment. The ground fault detection device 100 is a device that is connected to an ungrounded battery 300 and detects a ground fault in a system in which the battery 300 and the booster circuit 210 are provided. The ground fault detection device 100, the booster circuit 210, the load 360, and the like are controlled by the external control device 200 that is a higher-level device.

  Here, the insulation resistance between the output side of the battery 300, that is, the primary side positive electrode and ground is represented by RLp1, and the insulation resistance between the negative electrode and ground is represented by RLn1. Further, the insulation resistance between the output side of the booster circuit 210, that is, the secondary side positive electrode and ground is represented by RLp2, and the insulation resistance between the negative electrode and ground is represented by RLn2. The positive insulating resistance RLp is a combined resistance of RLp1 and RLp2, and the negative insulating resistance RLn is a combined resistance of RLn1 and RLn2. The combined low resistance of the positive electrode side insulation resistance RLp and the negative electrode side insulation resistance RLn becomes the system insulation resistance RL.

  The battery 300 is composed of a rechargeable battery such as a lithium-ion battery, the positive side is connected to the main relay MR+, the load 360 such as an electric motor via the booster circuit 210, and the negative side is the main relay MR. It is connected to the load 360 via −.

  As shown in the figure, the ground fault detection device 100 includes a capacitor C1 that functions as a flying capacitor. As the capacitor C1, for example, a ceramic capacitor can be used.

  Further, four switches S1 to S4 are provided around the capacitor C1 in order to switch the measurement path and control the charging/discharging of the capacitor C1. Further, a switch Sa for sampling a measurement voltage corresponding to the charging voltage of the capacitor C1 is provided. The switch Sa is turned on only during sampling. These switches can be composed of insulating type switching elements such as optical MOSFETs.

  The switch S1 has one end connected to the positive electrode of the battery 300 and the other end connected to the anode side of the diode D1. The cathode side of the diode D1 is connected to the resistor R1, and the other end of the resistor R1 is connected to the first plate of the capacitor C1.

  The switch S2 has one end connected to the negative electrode of the battery 300 and the other end connected to the resistor R5. The other end of the resistor R2 is connected to the second plate of the capacitor C1.

  The switch S3 has one end connected to the resistor R2 and the anode side of the diode D3, and the other end connected to the resistor R3 and one end of the switch Sa. The cathode side of the diode D3 is connected to the first plate of the capacitor C1, the other end of the resistor R2 is connected to the cathode side of the diode D2, and the anode side of the diode D2 is connected to the first plate of the capacitor C1. . The other end of the resistor R3 is grounded.

  The switch S4 has one end connected to the second polar plate of the capacitor C1 and the other end connected to the resistor R4. The other end of the resistor R4 is grounded. The other end of the switch Sa is connected to the A/D terminal of the control device 120.

  The control device 120 is configured by a microcomputer or the like, and executes various programs installed in advance to control various operations in the ground fault detection device 100. Specifically, the switches S1 to S4 are individually controlled to switch the measurement path, and the charging and discharging of the capacitor C1 are controlled. In addition, the charging voltage of the capacitor C1 is measured in each measurement path, the insulation resistance is calculated, and the ground fault is determined.

  Further, the control device 120 controls the switch Sa to input the analog level corresponding to the charging voltage of the capacitor C1 from the A/D terminal, performs a predetermined calculation based on this value, and calculates the insulation resistance RL. .. The measurement data and alarm of the control device 120 are output to the external control device 200.

  The ground fault detection device 100 of the present embodiment has, in addition to the same configuration as the conventional one described above, between the negative electrode of the battery 300 and the ground, that is, in parallel with the negative electrode side insulation resistance RLn via the normally open switch S5. The bypass resistor BR is connected. The bypass resistor BR may be connected to the secondary side. The switch S5 is switch-controlled by the control device 120 similarly to the switches S1 to S4.

  The bypass resistance BR is forcibly lowered by pulling down the insulation resistance on the negative electrode side when the current wraps around and becomes unmeasurable due to an increase in the boosted secondary voltage V2 when measuring Vcn. It is a resistance for enabling measurement of the side insulation resistance RLp.

That is, in the situation where current sneak occurs and measurement becomes impossible, the ground potential divided by the positive side insulation resistance RLp and the negative side insulation resistance RLn rises due to the rise of the boosted secondary side voltage V2 or the like. Is higher than the primary side voltage V1,
V1<(V2×RLn/(RLn+RLp))
Is when. This is a state in which the boosting ratio in the boosting circuit 210 is high and the positive insulating resistance RLp is lower than the negative insulating resistance RLn. For example, if the boosting rate is twice, measurement becomes impossible when the negative electrode side insulation resistance RLn>the positive electrode side insulation resistance RLp.

  Here, by lowering the negative electrode side insulation resistance RLn by the bypass resistance BR, the right side becomes smaller, so that the measurable range can be expanded. That is, it is possible to suppress a decrease in insulation resistance calculation opportunities.

  Since the negative resistance RLn is bypassed by the bypass resistance BR, the insulation resistance RL obtained at this time can be regarded as a combined resistance of the positive insulation resistance RLp and the bypass resistance BR. Since the value of the resistance BR is known, the relatively decreased positive electrode side insulation resistance RLp can be calculated from the obtained insulation resistance RL.

  If the value of the bypass resistance BR is too small, a ground fault occurs, and if it is too large, it does not contribute to the reduction of the negative electrode side insulation resistance RLn. Therefore, the value of the bypass resistance BR is determined in consideration of the maximum boosted voltage, the allowable minimum insulation resistance value, and the like. For example, it can be 1 MΩ.

  The operation of the ground fault detection device 100 having the above configuration will be described. In the following, it is assumed that the main relays MR+ and MR- are on.

  As shown in FIG. 2, the ground fault detection device 100 repeats the measurement operation with the V0 measurement period→Vcn measurement period→V0 measurement period→Vcp measurement period as one cycle. In any measurement period, the capacitor C1 is charged with the voltage to be measured, and then the charging voltage of the capacitor C1 is measured. Then, the capacitor C1 is discharged for the next measurement.

  In the V0 measurement period, a voltage corresponding to the voltage of the battery 300 is measured. Therefore, the switches S1 and S2 are turned on, the switches S3 and S4 are turned off, and the capacitor C1 is charged. That is, as shown in FIG. 3, the battery 300 and the capacitor C1 serve as the measurement path.

  At the time of measuring the charging voltage of the capacitor C1, the switches S1 and S2 are turned off, the switches S3 and S4 are turned on, the controller 120 performs sampling, and the capacitor C1 is discharged for the next measurement. The operation at the time of measuring the charging voltage of the capacitor C1 and the operation at the time of discharging the capacitor C1 is the same in other measurement periods.

  In the Vcn measurement period, a voltage that reflects the influence of the negative electrode side insulation resistance RLn is measured. Therefore, the switches S1 and S4 are turned on, the switches S2 and S3 are turned off, and the capacitor C1 is charged. That is, as shown in FIG. 4, the battery 300, the resistor R1, the capacitor C1, the resistor R4, and the negative electrode side insulation resistance RLn serve as a measurement path.

  In the Vcp measurement period, the voltage that reflects the influence of the positive electrode side insulation resistance RLp is measured. Therefore, the switches S2 and S3 are turned on, the switches S1 and S4 are turned off, and the capacitor C1 is charged. That is, as shown in FIG. 5, the parallel circuit of the battery 300, the primary side positive electrode insulation resistance RLp1 and the booster circuit 210 and the secondary side positive electrode insulation resistance RLp2, the resistance R3, and the capacitor C1 serve as a measurement path.

  Based on (Vcp+Vcn)/V0 calculated from V0, Vcn, and Vcp obtained during these measurement periods, the control device 120 of the ground fault detection device 100 refers to the table data created in advance and the insulation resistance RL. To calculate. Then, when the insulation resistance RL becomes equal to or lower than a predetermined determination reference level, it is determined that a ground fault has occurred, and an alarm is output to the external control device 200.

  Next, the insulation resistance calculation operation in the ground fault detection device 100 of the present embodiment will be described with reference to the flowchart of FIG. First, measurement in each measurement period is performed (S101). In the measurement of each measurement period, as described above, the measurement is performed with the V0 measurement period→Vcn measurement period→V0 measurement period→Vcp measurement period as one cycle.

  In order to determine whether or not the current sneak from the secondary side occurs, it is checked whether or not the measurement value in the Vcn measurement period is 0 (S102). Here, considering the influence of noise or the like, for example, if it is several tens mV or less, it is assumed to be 0.

  If the measured value in the Vcn measurement period is not 0 (S102: No), normal calculation is possible, and thus the insulation resistance RL is calculated based on the obtained measured value in each measurement period (S103).

  On the other hand, if the measured value during the Vcn measurement period is 0 (S102: Yes), the current sneak from the secondary side occurs, and normal calculation is impossible. Therefore, the switch S5 is turned on to bypass. The resistor BR is brought into the connected state (S104).

  Then, the measurement in each measurement period is performed with the bypass resistor BR connected (S105). That is, the measurement is performed with the V0 measurement period→Vcn measurement period→V0 measurement period→Vcp measurement period as one cycle.

  In the state where the bypass resistor BR is connected, it is checked whether or not the measurement value during the Vcn measurement period is 0 in order to determine whether or not the current sneak-up from the secondary side occurs (S106). Also at this time, for example, if it is several tens of mV or less, it is regarded as 0.

  If the measured value in the Vcn measurement period is not 0 with the bypass resistance BR connected (S102: No), the insulation resistance RL with the bypass resistance BR connected can be calculated, so The insulation resistance RL is calculated by the same calculation method (S107).

  However, the calculated insulation resistance RL can be regarded as a combined resistance of the positive insulation resistance RLp and the bypass resistance BR. Therefore, the positive-side insulation resistance RLp is calculated from RL=RLp×BR/(RLp+BR) without being treated as an insulation resistance for system ground fault determination (S108). It is possible to determine the ground fault on the positive electrode side from the calculated positive electrode side insulation resistance RLp.

On the other hand, if the measured value during the Vcn measurement period is 0 with the bypass resistance BR connected (S106: Yes), the insulation resistance cannot be calculated (S109). In this situation, the ground potential divided by the positive side insulation resistance RLp and the bypass resistance BR rises due to the rise of the boosted secondary side voltage V2, etc., and is higher than the primary side voltage V1. Is the case
V1<(V2×BR/(BR+RLp))
Is established.

For this reason,
RLp<BR×(V2-V1)/V1
Then, the maximum value RLpmax of the positive electrode side insulation resistance RLp can be calculated using the primary side voltage V1, the secondary side voltage V2, and the bypass resistance BR. This makes it possible to detect that the positive electrode side insulation resistance RLp is at least RLpmax or less. Here, BR*(V2-V1)/V1 on the right side of the above inequality means a value obtained by multiplying the value obtained by subtracting 1 from the step-up ratio by the bypass resistance BR.

  In addition, in order to calculate the maximum value of the positive electrode side insulation resistance RLp, it is necessary to obtain the step-up ratio in the step-up circuit 210. When the control device 120 of the ground fault detection device 100 cannot acquire these values, the external control device 200 may calculate the maximum value of the positive electrode side insulation resistance RLp. In this case, a part of the external control device 200 functions as the ground fault detection device 100.

  As described above, according to the ground fault detection apparatus 100 of the present embodiment, when the measured value in the Vcn measurement period is 0, the bypass resistance BR is connected and the measurement is performed. Therefore, the positive insulation resistance RLp The calculable range can be expanded. For this reason, in the system ground fault detection device including the booster circuit, it is possible to suppress a decrease in insulation resistance calculation opportunities.

  Further, even when the bypass resistor BR is connected, when the measured value in the Vcn measurement period is 0, based on the values of the primary side voltage and the secondary side voltage or the step-up ratio in the step-up circuit 210, the positive side insulation resistance RLp. The maximum value of can be grasped.

100 Ground Fault Detection Device 120 Control Device 200 External Control Device 210 Booster Circuit 300 Battery 360 Load BR Bypass Resistance C1 Capacitor RL Insulation Resistance S1, S2, S3, S4, Sa Switch

Claims (3)

A ground fault detection device for detecting a ground fault by connecting to a non-grounded battery that supplies power to a load via a booster circuit, and calculating an insulation resistance of a system in which the battery is provided,
A capacitor that operates as a flying capacitor,
A first switch connected between the positive electrode of the battery and the first plate of the capacitor;
A second switch connected between the negative electrode of the battery and the second plate of the capacitor;
A resistor and a third switch connected in series between the first plate of the capacitor and ground;
A fourth switch connected between the second plate of the capacitor and ground;
A bypass resistor and a fifth switch connected in series between the negative electrode of the battery and the ground;
A control unit that controls the first switch, the second switch, the third switch, the fourth switch, and the fifth switch, and is connected in series with the third switch. A control unit for measuring the voltage generated in the resistor,
The control unit controls ON/OFF of the first switch, the second switch, the third switch, and the fourth switch in a state where the fifth switch is turned off,
A V0 measurement path for charging the capacitor with the first switch and the second switch turned on and the third switch and the fourth switch turned off ;
A Vcn measurement path that charges the capacitor with the first switch and the fourth switch turned on and the second switch and the third switch turned off ;
A Vcp measurement path that charges the capacitor with the second switch and the third switch turned on and the first switch and the fourth switch turned off ;
The charging voltage of the capacitor is connected in series with the third switch with the third switch and the fourth switch turned on and the first switch and the second switch turned off. The charging voltage measuring path for measuring based on the voltage generated in the resistor, the charging voltage V0 of the capacitor charged in the V0 measuring path, and the charging voltage Vcn of the capacitor charged in the Vcn measuring path. , And a charging voltage Vcp of the capacitor charged in the Vcp measurement path,
When the measured value of the charging voltage Vcn of the capacitor is not regarded as 0, the ground fault is detected based on the measured values of the charging voltages V0, Vcn, and Vcp of the capacitor,
When the measured value of the charging voltage Vcn of the capacitor can be regarded as 0 , the first switch, the second switch, the third switch, and the fourth switch with the fifth switch turned on. By controlling the opening and closing of a switch, the V0 measurement path, the Vcn measurement path, the Vcp measurement path, and the charging voltage measurement path are switched, and the charging voltage of the capacitor charged in the V0 measurement path is switched. V0, the charging voltage Vcn of the capacitor charged in the Vcn measurement path, and the charging voltage Vcp of the capacitor charged in the Vcp measurement path are measured, and the charging is performed with the fifth switch turned on. A ground fault detection device that detects a ground fault based on the measured values of the voltages V0, Vcn, and Vcp . When the measured value of the charging voltage Vcn in the state where the fifth switch is turned on is not regarded as 0, the control unit controls the charging voltages V0 and Vcn in the state where the fifth switch is turned on . The ground fault is detected by calculating a positive side insulation resistance, which is an insulation resistance between the positive electrode of the battery and the ground , using the measured value of Vcp and the resistance value of the bypass resistance. Detection device. When the measured value of the charging voltage Vcn of the capacitor in the state where the fifth switch is turned on can be regarded as 0, the control unit is based on the step-up ratio of the step-up circuit and the resistance value of the bypass resistor. The ground fault detection device according to claim 1 , wherein the ground fault is detected by calculating a maximum value of a positive side insulation resistance that is an insulation resistance between the positive electrode of the battery and the ground .

Images